This invention relates to bottle closures for sealing bottles, and more particularly, to an injection molded bottle closure comprised of a first cellular structure of high density, a second cellular structure of relatively lower density, and a transitional cellular structure between the first and second cellular structures which provides for a gradual variation in cellular density.
Traditionally cork comprises the most common material for bottle closures. However, continued increases in demand for cork increase the cost of cork, and place a strain on the diminishing supply of cork producing trees. Further, variations in the color, compressibility, and rigidity of cork renders a substantial amount of cork unusable. Hence, there exists a need for a suitable alternative to natural cork bottle closures.
Synthetically generated bottle closures are well known in the art, some even utilize thermoplastic resins and blowing agents to create a dense outer skin and a low density interior. U.S. Pat. No. 5,692,629 disclose such a product. These type of bottle closures, however, suffer from several drawbacks. Synthetic bottle closures typically have rough outer surfaces. These surfaces prevent the bottle closure from forming a strong uniform seal of the bottle. A deficient seal allows for leakage of the contents of the bottle, and provides an opportunity for contaminates to enter the bottle. Additionally, the rough appearance renders the bottle closure less aesthetically pleasing. The rough appearance generally results from imperfections in the cellular structure of the bottle closure. Opens and fissures created during the injection molding process provide areas where contaminants can collect, and provide an environment for the growth of bacteria.
Furthermore, a bottle closure must ensure a hermetic airtight seal and provide for the removal of the bottle closure, and in some cases re-closure of the bottle. Thus, a bottle closure requires a degree of compressibility and a memory to allow the bottle closure to return to its original size. Cork, despite its other drawbacks, naturally possesses this quality. Synthetic bottle closures, even those that utilize blowing agents, lack compressibility and a memory for decompressibility. In other words, synthetic bottle closures lack the look and feel of cork. Accordingly, there exists a need for an injection molded bottle closure that can provide a hermetic airtight seal and at the same time maintain the look and feel of natural cork.